The invention is directed to a method and apparatus for connecting wire to circuit board-mounted, insulation displacement contacts (IDC).
Complex electrical circuits are sometimes constructed by interconnecting various electrical points of the circuits by means of insulation displacement contacts connected by wire runs, and various manual and semiautomatic tools for inserting the wire into the contacts have been proposed in the prior art. Representative of such prior art is the above-referenced U.S. Pat. No. 4,271,573, which discloses a hand-held tool for inserting the wire into various contacts of a stationary circuit board, according to a light ray system, in order to provide various wiring runs between the contacts. In order to terminate a particular wire run, several forms of cutting tools are disclosed as attachable to the insertion tool. The prior art has several disadvantages, namely: lack of automation; an inability to cut wire consistently and close enough to an IDC when terminating a run so as to prevent electrical shorting to an adjacent IDC, an inability to cut wire at the last insertion of a wire run while the tool is over the last contact, without the need for repositioning of the insertion tool; and the lack of a structurally sound and efficient cutting means attached advantageously to the insertion portion of the tool. The attached cutters in the prior art provide termination of the runs with an end portion of wire of approximately 0.040 inches protruding from the contacts, thus increasing the possibility of short circuits when the contacts are positioned or populated closely together upon a circuit board.
Accordingly, an object of the instant invention is to provide an insertion tool for forming wire runs, including "daisy chain" runs between contacts as required.
Another object of the instant invention is to cut the wire to terminate a run and prepare the remaining supply wire for additional runs.
An additional object of the invention is to provide automatic positioning of the circuit board or the insert head to align and orient an insulation displacement contact and a pusher of an insertion head relative to each other.
A further object of the invention is to feed and guide wire from a supply spool while eliminating any drag on the feeding as caused by inertia of the supply spool.
An additional object of the invention is to provide vertical reciprocation between the insert head and the circuit board to facilitate installation and removal of circuit boards when operating in an automatic mode.
Another object of the invention is to provide improved speed and accuracy in the wiring of such a circuit board, thus providing an increased cycle rate.
A further object of the invention is to eliminate steps in the termination of a wire run by eliminating the need to reposition the insertion head prior to performing the termination cutting step.
It is a further object of this invention to consistently terminate a wire run close to a contact with very little (i.e., on the order of 0.025 inches) of the wire extending past the contact in order to allow closer spacing of contacts dn a circuit board without electrical short-circuiting of the connected wires.
These and other objects will become apparent from a detailed description of the invention.
In summary, the invention is directed to a method and apparatus for connecting wire to insulation displacement-type, circuit board-mounted electrical contacts, and comprises automatic positioning and orienting of individual contacts relative to a wire insertion head so that a portion of wire is fed from a supply to the tip of a pusher of the insert head. The pusher inserts this portion of wire into the fingers of the contact to provide an electrical and mechanical connection. Another contact is positioned and oriented relative to the pusher to receive a second portion of the wire and provide a wire run between the contacts. The wire run can be terminated at the last contact without repositioning the contact and pusher relative to each other, with the remaining supply wire being prepared for another insertion.